Conceptual Demonstration of Ambient Desorption-Optical Emission Spectroscopy Using a Liquid Sampling-Atmospheric Pressure Glow Discharge Microplasma Source

Abstract

The concept of ambient desorption-optical emission spectroscopy (AD-OES) is demonstrated using a liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma as the desorption/excitation source. The LS-APGD has previously been employed for elemental analysis of solution samples and particulates introduced via laser ablation in both the optical emission and mass spectrometries (OES, MS) modes. In addition, the device has been shown to be effective for the analysis of elemental and molecular species operating in an ambient desorption/ionization mass spectrometry (ADI-MS) mode. Proof-of-concept is presented here in the use of the LS-APGD to volatilize three very diverse sample forms (metallic thin films, dry solution residues, and bulk materials), with the liberated material excited within the microplasma and detected via OES, i.e., AD-OES. While the demonstration is principally qualitative at this point, it is believed that the basic approach may find application across a broad spectrum of analytical challenges requiring elemental analysis, including metals, soils, and volume-limited solutions, analogous to what has been seen in the development of the field of ADI-MS for molecular species determinations.

Rapid Determination of Uranium Isotopic Abundance from Cotton Swipes: Direct Extraction via a Planar Surface Reader and Coupling to a Microplasma Ionization Source

“…There have been two previous approaches to direct surface analysis utilizing the LS-APGD. Analyte surfaces can be probed through the use of laser ablation (LA-LS-APGD) , or the surface can be sampled directly through an ambient desorption (AD) process. , LA into the microplasma suffers the same disadvantages as other laser-based techniques such as small sampling area and increased complication. While AD-LS-APGD is capable of directly analyzing the surface with a reasonably large sampling area (∼4 mm 2 ), the thermal component of the plasma causes the cotton swipes to burn.…”

“Insert-and-Go” Activated Carbon Electrode Tip for Heavy Metal Capture and In Situ Analysis by Microplasma Optical Emission Spectrometry

“…In this work, a small activated carbon electrode tip was used to capture heavy metals in the solution sample through a simple liquid–solid phase transformation and then used as an inner electrode of the coaxial DBD for in situ analysis of heavy metals by microplasma OES. Due to the large surface area, high adsorption capacity, porous structure, and various functional groups such as carboxyl, carbonyl, phenol, etc., activated carbon can enrich heavy metals through electrostatic attraction and surface complexation. − The DBD microplasma as an excitation source would make the elemental species on the surface of the activated carbon electrode tip go through a series of processes, including the conversion from the solid phase to gas phase, and atomization/excitation to produce characteristic spectral signals . For instance, Cd­(II) captured on the activated carbon electrode tip can be directly reduced through the electron transfer reaction to form volatile vapor between solid and microplasma interfaces, ,, and then excited by microplasma electrons to produce the corresponding characteristic emission lines (Figure a).…”

“…In contrast, tungsten coil-based ETV for sample introduction into the microplasma is inclined to achieve simultaneous determination of multiple elements, but the limited sample loading volume on the tungsten coil hampers the further improvement of sensitivity, and the usable life of tungsten coil limits long periods of operation. Marcus et al presented a proof-of-concept using the liquid sampling-APGD to volatilize and excite dry solution residues and detected heavy metals via OES . While the demonstration is principally qualitative, it would be of significance for fast field analysis if heavy metal residues could be accurately analyzed.…”

“…Marcus et al presented a proof-of-concept using the liquid sampling-APGD to volatilize and excite dry solution residues and detected heavy metals via OES. 26 While the demonstration is principally qualitative, it would be of significance for fast field analysis if heavy metal residues could be accurately analyzed. It remains a challenge to achieve highly sensitive OES detection of heavy metals by in situ excitation of analytes deposited on the substrate surface with microplasma, and the key lies in how to improve the sample introduction into microplasma.…”

Alternating-Current-Driven Microplasma for Multielement Excitation and Determination by Optical-Emission Spectrometry

“…Microplasma is produced by confining the dimension of plasma to 1 mm or less . Currently, various configurations of microplasma have been applied for optical emission, including glow discharge (GD), − microhollow-cathode discharge (MHCD), , dielectric-barrier discharge (DBD), − point discharge (PD), , capacitively coupled microplasma (μCCP), microfabricated inductively coupled plasma (mICP), and microwave-microstrip plasma (MSP) . Compared with conventional inductively coupled plasma (ICP) as the excitation source, microplasma possesses a series of excellent characteristics, including simplicity, a small size, a nonthermal source, and low power and gas consumption .…”